Oral Submission Presentation by Blake Foster - New Zealand ...

EXECUTIVE SUMMARY
The problem
Wilding conifers have been invading Pukaki Downs station since the early 1960s . Initially, invasion was
restricted to a short section of the lakeshore by the Homestead, but more extensive invasion started to
take hold in the late 1980s / early 1990s. The main spreading species is Lodgepole or contorta pine
(Pinus contorta), the country’s most vigorous spreading conifer. At the present time, wildings are
approaching canopy closure over approximately 30-40% of the station, with much of the remaining area
affected by widely scattered outlier trees (often accompanied by patches of fringe spread). If left
unmanaged, wildings would dominate the majority of Pukaki Downs. Hence, the owners are attempting
to manage the spread by containment within the areas least likely to spread further, and removal of
wildings from areas with higher risk of distant spread.
Client Initiative
In April, 2010, Nick Ledgard (NL) of Scion in Christchurch was asked by Blake Foster of Pukaki Tourism
Holdings Ltd to carry out a field inspection and write a report on the wilding conifer situation and
management options on Pukaki Downs station. NL visited the station from May 30 – June 2, 2010, after
which he wrote this report.
The project
The major objectives of this report are to describe:
a) the history of conifer spread, its origin and present location
b) the likely future spread risk and pattern if left unmanaged
c) priority control areas for minimising spread risk beyond present locations (particularly off-station)
d) options for containing conifers within the managed areas.
e) areas with least spread risk which could be managed for carbon storage.
Key Findings
o The wilding conifer problem along the south-western shores of Lake Pukaki is well
known, situated alongside a major tourist route (SH80). Unfortunately, it involves
the most spread-prone conifer species, contorta pine.
o Wildings have been spreading since the 1960s, but the area obviously affected
has only increased significantly in the last 15 years. This has been largely
triggered by spread from the lake-shore plantings carried out after the lake was
raised in the early 1970s, although most of the contorta forests in the southeastern
portion of Pukaki Downs originate from trees present before that time.
o The pattern of spread likely in the future is well indicated by the pattern of spread
over the last few decades. These show that spread is mainly to the south, driven
by the prevailing strong northerly winds, but that occasionally a more northeasterly
wind can pick up and carry seed high into the air and more to the west.
o Such an event in the early 1990s gave rise to outlier wildings in the upper Twizel
river catchment, which were allowed to mature and cone before they were
removed in the mid 2000s, giving rise to the islands of fringe spread so obvious
today.
o The ‘one-off’ nature of this spread event indicates that once the Twizel river flats
are cleared, they should not be re-invaded often and hence should not be too
difficult to keep clear in the future – as long as any wilding trees which do establish
are removed before age 5-6, when they begin coning.
o This ‘stitch-in-time-saves-nine’ maxim must always be kept foremost in any
management plan.
o Within the wilding cleared zones, a containment area of trees will remain.
o Removal sweeps outside the containment area will be needed at least every 4
years for as long as seeding contorta pine trees remain in the locality.
o The incidence of re-invasion, and need for timely removal, should be diminished by
the control and containment management options recommended below.
(i)